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Ultra supercritical high-efficiency power generation technology

Become a popular vocabulary

So what kind of superpowers does this technology have?

Ultra supercritical high-efficiency power generation technology

It is the clean and efficient utilization of coal resources

Can be used for building new units

It can also be used to renovate old units

Squeeze coal dry and clean

Generate more electricity with less coal

Achieve resource conservation

The purpose of improving efficiency and reducing emissions

What is ultra supercritical high-efficiency power generation technology

Ultra supercritical refers to the state of a medium. In the field of coal-fired power production, it refers to the state of water. The higher the parameters such as steam pressure and temperature, the higher the energy efficiency. At a pressure of 22.115 megapascals and 374.15 ℃, the density of water vapor will increase to the same level as liquid water, and this condition is called the critical parameter of water. A parameter higher than this is called a supercritical parameter, while a steam temperature in the furnace not lower than 593 ℃ or a steam pressure not lower than 31 megapascals is called ultra supercritical. The power generation technology that uses such steam to drive the steam turbine unit to do work is the ultra supercritical coal-fired power generation technology.

Still don't understand? Let's start understanding from the critical point.

Any pure substance has a critical point, for example, at atmospheric pressure, water will vaporize into water vapor after heating to 100 ℃ and continuing to heat; When the pressure of water exceeds 22.13 megapascals (approximately 221 times atmospheric pressure) or the temperature exceeds 374.15 ℃, vaporization and condensation processes no longer occur.

Critical state

At critical pressure or critical temperature, pure substances are in a "critical" state.

Subcritical state

Below the critical pressure or temperature, it is in a "subcritical" state.

Supercritical state

Above the critical pressure or critical temperature is the 'supercritical' state.

Conventional thermal power generation units (including coal-fired power generation, biomass power generation, etc., excluding gas-fired power generation) use coal and other fuels to burn in boilers, heating and boosting water into high-temperature and high-pressure steam, driving the turbine to rotate at high speed, and then driving the generator to generate electricity.

According to the laws of thermodynamics, the efficiency of converting thermal energy into electrical energy in the process of thermal power generation increases with the increase of boiler outlet steam temperature. In actual processes, it is necessary to synchronously increase steam pressure, unit capacity, etc. to comprehensively improve system efficiency.

After hundreds of years of development, thermal power generation units have generally gone through the following states.

Among them, the initial parameters of supercritical, ultra supercritical, and advanced ultra supercritical units under development are all in a supercritical state, while the initial parameters of other levels of units are in a subcritical state.

Strictly speaking, pure substances only have three states: "critical," "subcritical," and "supercritical," and there is no such thing as "ultra supercritical. The ultra supercritical parameters are essentially parameters that are one level higher than the previous supercritical parameters, and belong to the range agreed upon by the industry. The so-called "ultra supercritical power generation technology" refers to the efficient power generation technology that uses a feed pump to increase the pressure of water to ultra supercritical pressure, and then heats the water to ultra supercritical temperature through fuel combustion in a boiler, and generates electricity through a steam turbine generator set.

Ultra supercritical power generation technology is currently the most advanced thermal power generation technology in the world, which can simultaneously achieve ultra-low emissions of pollutants while reducing the coal consumption rate of power supply to below 265 grams per kilowatt hour.

The tortuous development has gone through seventy years

The concept of ultra supercritical power generation is not new in the technical field. Since its initial proposal, it has been developing globally for more than 70 years and can be roughly divided into three stages.

first phase

Since the 1950s, represented by the United States, Germany, and the former Soviet Union, ultra supercritical power generation technology has been directly developed without experiencing the transition of supercritical parameters. However, due to frequent failures of many ultra supercritical units, starting from the late 1960s, these countries generally lowered the steam parameters of newly built units to the supercritical range.

phase 2

Since the early 1980s, supercritical technology has been consolidated and developed. With the development of material technology, especially the significant improvement of material properties for boilers and steam turbines, as well as a deeper understanding of water chemistry in power plants, the series of fault problems encountered by early supercritical units have been overcome one by one.

Third Stage

Since around the 1990s, ultra supercritical power generation technology has been revitalized. With the increasingly strict environmental requirements internationally, as well as the successful development of new materials and the maturity of conventional supercritical technology, the development of ultra supercritical technology has better conditions. Represented by technologies from Japan (Mitsubishi, Toshiba, Hitachi) and Europe (Siemens, Alstom), adopting higher steam temperatures and pressures has become the mainstream trend in the development of thermal power technology while ensuring high reliability and availability of the units.

In China, the application of ultra supercritical technology started relatively late, but its development speed is rapid. At present, ultra supercritical high-efficiency power generation technology and demonstration projects have been promoted nationwide, accounting for 26% of the total installed capacity of coal-fired power plants. China is already the country with the fastest development, largest quantity, largest capacity, and most advanced operational performance of 1000 MW ultra supercritical units in the world.

Continuous breakthroughs in technological means

The development of ultra supercritical units towards higher parameter technology requires further improvement of the temperature and pressure of the boiler outlet steam. The current supercritical alloy materials can withstand a temperature range of up to 630 ℃. To further increase the steam temperature at the boiler outlet, it is necessary to develop more advanced alloy materials that can withstand higher temperatures, and to minimize the use of expensive high-temperature resistant alloy materials through system research and development such as welding and manufacturing processes, while ensuring safety. Therefore, material costs and key equipment manufacturing processes are currently the biggest obstacles affecting 700 ℃ ultra supercritical power generation technology.

To further improve the efficiency of the unit, the National Energy Administration has established the China 700 degree Celsius Ultra supercritical Coal fired Power Generation Technology Innovation Alliance, relying on the Phase III 2 × 660 MW expansion project of Guoneng Jinjie Company to carry out related research activities, so that the unit efficiency can reach over 50%.

During the period, high-level layout technology was proposed, which means raising the operating platform of the steam turbine generator unit from the conventional 13.7 meters to 65 meters, arranging the coal bunker and deaerator equipment in a new pattern at the lower part of the main plant, and shortening the high-temperature steam pipeline.

Compared with conventional units, the high-level layout project can reduce the mass of the four major pipelines by 259.5 tons, with a savings rate of 30.93%. The main plant building can also reduce its footprint by about 50%, playing a leading demonstration role in the development of 700 degree Celsius ultra supercritical coal-fired power generation technology.

The dual goals of carbon peak and carbon neutrality are an energy revolution. As one of the main technologies for energy conservation and emission reduction in thermal power, ultra supercritical power generation technology is an important way to achieve high-quality development of energy and electricity in China's basic national conditions of rich coal, poor oil, and limited gas.

China has been continuously developing million kilowatt ultra supercritical high-efficiency power generation technology for 15 years. At present, the lowest coal consumption for power supply can reach 264 grams per kilowatt hour, which is significantly lower than the national average and at the forefront of the world.

reference:

[1] She Huimin What are the superpowers of ultra supercritical power generation? [N] Economic Daily, 2022-06-12 (005)

[2] Li Yan argued The Minister of Science and Technology has repeatedly mentioned "ultra supercritical high-efficiency power generation technology" [N]. Shanghai Securities Journal, 2022-06-07 (001)

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Original title: "What are the superpowers of ultra supercritical power generation technology